Room-temperature fluoride ion batteries based on LDH@PPy composites

Fluoride-ion (F⁻) batteries (FIBs) are a high-energy, cost-effective and safe alternative to lithium-ion batteries because of multiple-electron redox reactions, abundance of resources and absence of dendrite issues. Layered double hydroxides based on transition metals offer intriguing promise as F⁻-storage electrodes but suffer from poor electrical conductivity. Herein, a new cathode material of FIBs was synthesized by in situ polymerization of pyrrole monomers on the surface of F⁻ intercalated CoNi LDH (CoNi-F⁻-LDH) platelets. Without destroying its 2D channel and anion storage capacity, the overall electrical conductivity of CoNi-F⁻-LDH is improved. The resulting polypyrrole (PPy) coated CoNi-F⁻-LDH exhibits a reversible capacity of ∼ 60 mAh/g over 100 cycles at room-temperature, with a capacity retention of 86 %, superior to most of previously reported cathodes for FIBs. This work illustrates a potential pathway for updating LDH electrodes for room-temperature FIB chemistries.